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Djokovic achieved the top ranking in July 2011 and has been mostly No. 1 ever since

But Djokovic is now in danger of losing the No. 1 ranking to a surging Rafael Nadal

Djokovic and Nadal are competing at next week's China Open in Beijing

Novak Djokovic admitted that this year could have been better for him at the grand slams. He won the Australian Open but lost two finals and had clay-court king Rafael Nadal on the ropes at the French Open.

Djokovic, though, had reason to celebrate Monday as he became just the ninth man to spend at least 100 weeks at No. 1 on the tennis tour.

Djokovic achieved the top ranking in July 2011, taking over from Nadal, and has mostly held down the No. 1 position ever since.

When he caught Nadal two years ago, it marked the first time since 2004 that the Spaniard or Roger Federer wasn't at the summit.

"I was taught to dream big and to dream to be No. 1 in the world," Djokovic told the ATP website. "It takes years of hard work and dedication.

"It is a long process to become a champion. Tennis is a very specific and unique sport, where you take all the credit or all the blame."

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Djokovic's major breakthrough came in 2011, when he claimed three of the four majors and started the campaign with 41 consecutive victories.

Although he only landed one grand slam title in both 2012 and 2013, Djokovic appeared in a 14th straight grand slam semifinal in New York this month, moving him more than halfway past Federer's impressive record of 23.